1. Field of the Invention
The invention relates to a portable power with available AC power, particularly to a boost control circuit to charge lithium batteries by a boost charging method and to an AC/DC power output modulation circuit to prevent instant surge and high-current feedback.
2. Description of the Related Art
Due to the growing popularity of portable electronic products, standby power becomes very important; therefore, portable power is made for the portable electronic products.
The portable power is composed of lithium batteries which should be well-protected while using the portable power. For example, when there is an instant surge or high-current feedback, power from the batteries will be cut by a protection circuit.
FIG. 1 illustrates a battery protection circuit 10 connected to a battery pack B, comprising, a control module 11 and a Metal-Oxide-Semiconductor Field-Effect Transistor, hereinafter referred to as MOSFET circuit module 12. The MOSFET circuit module 12 includes a discharge MOSFET 121 and a charge MOSFET 122. The control module 11 is provided for detecting charge/discharge current and voltage of the battery pack B and controlling the gates of the discharge MOSFET 121 and the charge MOSFET 122. While a DO pin 111 and CO pin 112 output high voltages, the MOSFET circuit module 12 is in an ON state and the battery pack B is charging or discharging. In the discharging process, the voltage will be gradually reduced. While the control module 12 detects the battery voltage below a preset value, the DO pin 111 outputs low voltage and the discharge MOSFET 121 is in an OFF state to cut the discharge circuit to achieve protection function. However, the battery protection circuit 10 cannot restore power supply after cutting the output power, resulting in an inconvenience use.
Moreover, the conventional portable power only provides DC power and the conventional lead-acid batteries are heavy and thick. The conventional portable power cannot be charged in the outdoor or charged by the car cigarette lighter, without a transformer.
FIG. 2 illustrates a power supply 20, comprising a capacity 21, a full-wave rectifier 22, and a π-type filter 23 connected to the full-wave rectifier 22, and an electrical product 27 connected to the π-type filter 23. The π-type filter 23 includes a resistive fuse 24, a first capacity 25 and a second capacity 26. The π-type filter 23 is connected to the resistive fuse 24 in series for filtering out clutter of AC power. When the voltage of the DC power supply exceeds the rated value, the resistive fuse 24 is damaged and power is cut off to protect the electrical product 27 connected to an output terminal of the π-type filter 23.